There is a new update of the CSOM API for SharePoint and Project Online available:
There is now support for cost rate tables more or less similar to the PSI functionality:
Following properties, classes and methods have been added.
That's great, but excuse me, what about on-premise msp 2016?
In June SU MS has updated the client library for on-premise in order to support Cost rate table support
Now you can use Microsoft.ProjectServer.Client.dll with Enterprise Resources Cost rates.